1. Field of the Invention
This invention generally relates to a device for supporting a user in a seated position, and in one preferred embodiment, to a chair of the reclining back type. In another preferred embodiment, this invention relates to a chair having automatically adjusting armrests. In a further prefer-red embodiment, this invention relates to a chair having an adjustable headrest. In a still further preferred embodiment, this invention relates to a chair having an automatically adjusting resistance to tilting that increases in proportion to the weight of the user and as the tilt angle is increased. In a yet further preferred embodiment, the chair has a tilting mechanism which changes the angle of the seat and its support and increases the chair""s angle of maximum recline, as well as providing a forward tilting position.
2. Description of the Related Art
Reclining type chairs commonly used in offices usually provide for the back to recline alone, for the seat and back to recline as a unit, or the seat back may recline in a coordinated proportion with the seat. If the back alone pivots, it generally creates a problem known as xe2x80x9cshirt tail pull.xe2x80x9d This problem is particularly acute if the pivot of the chair back is not coordinated with the natural body action. This problem can also be accentuated by the tendency of the hips of the user to slide forward as the back tilts rearwardly.
In chairs where both the seat and back recline as a unit, in the reclined position there is a tendency to lift the legs of the user from the floor creating an undue pressure by the forward edge of the seat against the underside of the legs of the user immediately above the knee. To overcome this problem the pivot point of the reclining action may be moved forward sufficiently to permit the user""s feet to stay on the floor. The undesirable effect of this arrangement is that the body angle between the user""s torso and legs is unchanged and as a result, the user""s eye level drops undesirably when the chair is reclined.
In any reclining chair, it is desirable that the recline pivot point be at the center of the body or where the user""s back normally pivots (i.e., an axis through the user""s hip joints). The pivot point of a reclining chair is normally displaced from the ideal pivot point. It is also desirable to have a chair wherein the angle between the user""s torso and his legs opens up to relieve internal congestive body pressures. It is, of course, also desirable to provide a chair wherein the user""s feet remain on the floor and the recline action parallels the natural body action closely enough to avoid the common shirt tail pull problem.
It is also desirable to provide a chair which is of simplified construction and yet of clean, pleasing appearance emphasizing the isolated and separate appearance of the seat and back with respect to the supporting frames.
My earlier U.S. Pat. No. 4,429,917 shows one approach to solving these problems. U.S. Pat. No. 4,943,114 to Piretti allegedly reports a chair with a compact backrest linkage mechanism that enables the chair backrest and seat to recline. U.S. Pat. No. 5,251,958 to Roericht et al. allegedly reports a chair with a synchronous adjusting device that uses the weight of the user to provide a restoring force to return the chair back to an upright position after a user has reclined in the chair.
U.S. Pat. No. 5,486,035 to Koepke, et al., asserts, without providing any showing, that xe2x80x9cIn such constructions, the difficulty of reclining the chair, i. e., generating the reclining force, increases the further the chair is reclined, and it is common to employ adjusting apparatus for increasing or decreasing the reclining tension of a chair, such adjusting apparatus changing the tension of a spring, or otherwise modifying the reclining mechanism.xe2x80x9d Col. 1, 1. 29-34.
While chairs with arms are well known in the art, heretofore, the arms have been either fixed, or adjustable. If the arms were adjustable, any adjustments have been less than ideal and/or quite cumbersome.
Additionally, it was known in the art to put a headrest on a chair, including a reclinable chair. However, such headrests typically provided the chair occupant with very little support, i.e., when the chair is reclined, the headrest maintains its position relative to the back of the chair. Alternatively, if the headrest were to provide the chair occupant with substantial support, the headrest required awkward adjustments.
Moreover, while it is believed that some reclining chairs heretofore available have had a means to adjust their resistance to reclining, such adjustments have been less than ideal, and/or very cumbersome and not practicable.
Instead, rather than confront the processes necessary to adjust their chairs to fit the needs of their particular body build, most users of chairs use them without making any adjustments. Consequently, any ergometric advantages that might be delivered by the properly tuned chair are not achieved. Thus, there remains a need for a chair that is adjustable to the needs of the individual chair occupant without requiring any substantial effort on the occupant""s part to effect the adjustments. In other words, a substantially self-adjusting ergometric chair.
It is an object of one embodiment of the present invention is to provide an occupant-weight-operated chair having a reclinable back wherein the chair is of a simple economical construction and lends itself to high production manufacturing and fabrication procedures.
A further object is the provision of a tilting chair wherein the frame supporting the seat and back are pivotally connected to the seat and fixedly connected to the back in a manner to emphasize the isolated and separate appearance of the seat and back.
An alternative object is to provide armrests that are readily adjusted.
These and other objects and advantages of the invention will become apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the invention may be employed.
Among advantages, some embodiments of the present invention provide an occupant-weight-operated chair having a reclining back wherein the occupant""s weight loads the chair mechanism and automatically adjusts the reclining tension or force to recline the chair back. In a further preferred version of such embodiments, this occupant-weight-operated chair provides a substantially uniform force opposing the reclining of the chair back throughout its range of movement. Moreover, while this mechanism includes a spring, it does not rely on a spring or other adjustment to increase or decrease the chair reclining force. Instead, the spring merely provides a secondary or auxiliary force to the force provided by the user""s weight. The spring does not require any adjustment.
An occupant-weight-operated chair in accord with the inventive concepts includes a chair having a seat and a back mounted upon support structure, such as a caster-mounted pedestal. The back is reclinable with respect to the seat, and the structure of the chair, and the relationship of the components, is such that as the back is reclined the entire seat raises against the weight of the occupant. In this manner, the occupant""s weight loads the chair mechanism, and the force required to recline the back is substantially uniform throughout the back-reclining range of movement, such force being regulated by the weight of the occupant upon the seat rear portion. In turn, through the connecting top links, lifts the entire seat a small amount, typically between about a quarter of an inch to an inch. Preferably, the seat is lifted by between about a half and three quarters of an inch.
Furthermore, the inventive occupant-weight-operated chair with a reclinable back attaches the back to the seat rear region so that reclining the back raises the elevation of the seat rear region against the occupant""s weight. The combination of the upward movement of the chair seat in conjunction with the reclining rotation of the chair back simulates the movement of the user""s torso about the user""s hip joint as the user reclines.
Some other embodiments of the present invention provide a tilting chair wherein the back is theoretically pivoted relative to the seat at or in alignment with approximately the ideal pivot point of the body of a user (for reclining the back, the ideal pivot point corresponds to a horizontal axis through the user""s hip joint). In addition, the seat lifting is coordinated with the back recline to simulate the natural action of the reclining body.
In another embodiment, the present invention provides a chair occupant with a headrest support that adjusts to provide the support when support is needed and to retract to an out of the way position when not needed.
In still further embodiments of the present invention provides a chair occupant with armrests that readily, and simply adjust to deliver support to the user through a greater range of useful positions than was available through the armrests that have been heretofore available. Such support should be provided when and as needed by the chair occupant.
A yet still further embodiment of this invention provides a variable resistance to recline of the back as the adjustable mechanism is tilted forward or rearward. In the forward tilted mode there is less resistance to recline and more resistance in the rearward tilted mode. These changes are effected automatically without adjustment being required by the user.
Some preferred embodiments of a tilting chair of the present invention have a base that pivotally supports a seat with opposite links of a two four-bar linkage mechanisms. Typically, in such embodiments, one set of the opposite links on each side of the chair extends to support the back. Additionally reclining chair embodiments of the present invention usually have a base that forms a fixed bar of the linkage. This linkage translates the actuation of the rear links into a change in the angle of the forward links.
Some of the reclining chairs of the present invention have a spring in the base which acts on one of the bars of the linkage is operative to urge the chair to an upright position. This spring also provides some assistance to counterbalance the user""s recline force.
Desirably, the chair lift mechanism of a reclining chair of the present invention is not normally noticed by the user, nor does such a chair lift the user""s feet off of the floor.
With the present invention, a tilting chair is provided wherein the seat back pivot is effectively at the ideal point and which obviates the problems of shirt tail pull and feet lift common in prior art chairs. The present invention provides a chair in which both the seat and back are supported from the base by a linkage mechanism which permits the tilting of the back to increase the angle of the user""s torso to his legs.
This reclining of the seat and back can be achieved with a four-bar linkage. The four-bar linkage can be parallel or non-parallel. In one embodiment of the inventive chair, the seat is supported on each side by one of the links or cranks of the four-bar linkage. The base of the chair forms a second link, or crank. The third link, or crank, extends to support the chair back. The fourth link couples the forward portion of the base to the forward portion of the seat.
The linkage is duplicated on each side of the chair.
The pivots of the linkage are designed so that the body weight tends to balance the seat pivot and a spring within the base is operative on one of the bars of the linkage to urge the chair to an upright position, simply to overcome the weight of the chair and maintain an unoccupied chair in an upright position.
Typically, when the chair is reclined by a user, the spring adds a small amount of return force. However, as the body weight of the user determines the amount of force necessary to return the chair to the upright position, and thus this force will vary among users and the degree of recline, the chair of the present invention uses the body weight of the user to counter-act the user""s recline.
The bars of the linkage on each side of the chair are pivotally connected to the seat and the extended bar is fixedly connected to the back in a manner to emphasize the isolated and separate appearance of the seat and back.
Typically, the base spaced below the seat is of relatively small clean and compact construction housing the lower journals for the above-noted third and fourth links. In addition, the base houses the spring and a vertical height adjustment mechanism.
The horizontal links above the base are rails on which the seat pan is supported within guide tracks so the seat may be slid back and forth to adjust seat depth. The position of the seat within the guide tracks is fixed by a conventional mechanism.
Preferably, the back and seat portions are formed of a molded, stiffly flexible and resilient, synthetic plastic material, such as a reinforced glass fiber or other high strength material capable of flexing. The seat includes an upper, underside, front, and rear portions. Likewise, the back has an upper, lower, front, and rear portions. The Upper portion of the seat and the front portion of the back are typically contour molded and covered by a conventional cushioning material.
The underside of the seat front region (typically at the front of the rails that support the seat pan or support) is connected to the base by a pivot, and the underside of the seat rear portion is connected via a link to the lower region of the back.
As the seat reclines, and the rearward links (typically extensions of the back support) pivot about the rear pivot points on the chair base. As a result of the this pivoting, the pivot points under the seat support are raised slightly upwardly and rearwardly. The action of the seat support moving in this upward and rearward manner pulls the forward link (e.g., the upper horizontal seat support rails) so as to raise the forward portion of the seat. This lifting of the seat against the occupant""s weight, accordingly, uses the occupant""s weight to xe2x80x9cloadxe2x80x9d the back to resist the reclining forces. As a result, a seat constructed in accordance with this aspect of the invention has a substantially uniform resistance to reclining due to the fact that it is the occupant""s weight which produces such resistance. As the reclining tension is adjusted by the weight of the occupant, the greater the occupant""s weight, the greater the force required to recline the seat back, and vice versa.
In some embodiments of the present invention, the chair has one or two adjustable armrests. The adjustable armrests are supported by a pair of rods the originate in the back of the chair. Preferably, the adjustable arm support rods originate from an xe2x80x9cexoskeletonxe2x80x9d that holds the back of the chair. While it is most preferred that the chair having the adjustable arms is the reclinable chair of this application, the adjustable arms of the present invention can be adapted to most any chair having a back.
In a particularly preferred embodiment, the arms are readily raised or lowered. To disengage an arm, and permit it to be repositioned, the distal end of the armrest is raised by a slight amount, say about a centimeter. Once the positioning mechanism is disengaged, the arm can be readily repositioned to any height. When positioned, the arm is released and it falls into place, re-engaging the positioning mechanism. In one embodiment of this adjustable arm invention, a chair has two arms that are independent of each other. In an alternative embodiment of the adjustable arm invention, the movement of one arm adjusts the second arm a corresponding amount in the same direction.
In a particularly preferred embodiment, the chair has a headrest that moves forward to support the chair occupant""s head as the chair is reclined back and retracts as the chair returns to its upright resting position. In this manner, the chair occupant""s head is supported when the support is most needed, i.e., during full recline when the occupant""s head is not aligned with the occupant""s back. However, when the support is not needed, i.e., in the upright position when the occupant""s head is aligned with the occupant""s back, the support is moved out of the way. It is preferred that the headrest moves on an arc that mimics the natural movement of the head.
While it is most preferred that the chair having the automatically adjusting headrest is the reclinable chair of this application, the automatically adjusting headrest of the present invention can be adapted to most any chair having a reclinable back.
In yet another particularly preferred embodiment, an alternate support mechanism may be used in the base or lower link position that allows the entire chair above the base to be tilted forward or to the rear and locked in any position, i.e., either extreme or at any position between these extremes. This alternate support mechanism provides forward tilt for seat and back for work positions, such as writing, and the rearward tilt provides additional recline to the backrest.
From time to time, the term xe2x80x9cresting positionxe2x80x9d is used herein to refer to the upright or forward tilt position of the unoccupied chair.